Drive device for electric vehicle

ABSTRACT

The present structure does not require a knuckle on the vehicle body side, improves rotational accuracy of an input shaft of a speed reduction unit, increases durability of bearings, and suppresses rotation noise of the bearings by improving the supporting structure of the input shaft of the speed reduction unit. In a drive device for an electric vehicle comprising: a speed reduction unit including an input shaft driven by an electric motor; a hub unit rotationally driven by an output member of the speed reduction unit; and a housing accommodating the electric motor and the speed reduction unit, wherein the input shaft of the speed reduction unit is supported by bearings provided at two locations in the axial direction, the drive device is configured such that the bearings provided at the two locations are both supported by the output member, and the housing is provided with a suspension joining portion.

TECHNICAL FIELD

The present invention relates to a drive device for an electric vehicleincluding an electric motor as a drive source, and particularly to adrive device for an electric vehicle of an in-wheel motor type.

BACKGROUND ART

A conventionally known drive device for an electric vehicle of anin-wheel motor type is made up of an electric motor, a speed reductionunit to which the output of the electric motor is inputted, and a hubunit which is rotationally driven by the speed-reduced output of thespeed reduction unit (Patent Literature 1).

In the drive device for an electric vehicle disclosed in PatentLiterature 1, an electric motor is disposed outside the speed reductionunit in the radial direction, and the speed reduction unit in whichplanetary gear-type units are disposed in two stages in the axialdirection is used. The reason why the speed reduction unit is disposedin two stages is for the purpose of increasing the speed reductionratio.

A typical configuration of a speed reduction unit of planetary gear typeis such that a sun gear is provided on an input shaft in a coaxialmanner, and a ring gear is secured around the input shaft in a coaxialmanner. A plurality of pinion gears are placed between the sun gear andthe ring gear, and a pinion pin that supports each pinion gear is joinedto a common carrier. The carrier is integrated with an output member.

The speed reduction unit is configured such that the pinion gear iscaused to revolve while rotating on its axis by the rotation of theinput shaft. The rotational speed of the revolving motion is reducedfrom the rotational speed of the input shaft, and a speed-reducedrotation is transferred to the output member via the carrier. The speedreduction ratio in this case will be Zs/(Zs+Zr). Where, Zs is the numberof teeth of the sun gear, and Zr is the number of teeth of the ringgear.

The input shaft of the speed reduction unit is supported by bearingsdisposed at two locations in the axial direction, that is, aninboard-side bearing and an outboard side bearing. The inboard-sidebearing is attached to a housing of the speed reduction unit, and theoutboard-side bearing is attached to the output member of the speedreduction unit. The housing is supported by the vehicle body via thesuspension, and the output member is coupled and integrated with aninner member of the hub unit to rotationally drive the vehicle wheel.

In the above-described drive device for an electric vehicle, the radialload acting on the input shaft of the speed reduction unit is supportedby the housing via the inboard-side bearing on the inboard side, and issupported by the output member of the speed reduction unit via theoutboard-side bearing on the outboard side.

On the other hand, the hub unit is joined to a suspension via a knuckleon the vehicle body side in a normal motor vehicle driven by an internalcombustion engine.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 2001-32888

SUMMARY OF INVENTION Technical Problem

Regarding the supporting structure of the input shaft of the speedreduction unit, while vibration and impact associated with the rotationof the vehicle wheel are transmitted to the outboard-side end portion ofthe input shaft via the output member and the outboard-side bearing,vibration and impact of the vehicle wheel will not be directlytransmitted to the inboard-side end portion since it is supported by astationary housing via the inboard-side bearing.

Moreover, since the hub and the hub bearings that support the outputmember of the speed reduction unit elastically deform due to the effectof the load imposed on the vehicle wheel from the road, theoutboard-side bearing is displaced with respect to the original centerof the input and output shafts. On the other hand, the housing thatsupports the inboard-side bearing is not likely to be affected by theload from the vehicle wheel, and therefore the coaxiality between thetwo bearings that support the input shaft deteriorates or theinclination therebetween occurs.

For this reason, eccentric load is likely to act on the inboard-sidebearing and the outboard-side bearing, thus causing problems such asdecline of rotational accuracy of the input shaft, deterioration of thedurability of the bearings, and occurrence of rotation noise of thebearings.

Moreover, in an electric vehicle, since conventionally a knuckle is arequired member in the joining structure between the hub unit and thesuspension on the vehicle body side, the number of parts is increasedaccordingly.

Thus, it is an object of the present invention to provide a structurethat does not require a knuckle on the vehicle body side while improvingthe rotational accuracy of the input shaft and the durability of thebearings and suppressing the rotation noise of the bearings by improvingthe supporting structure of the input shaft of the speed reduction unit.

Solution to Problem

To solve the above-described problems, the present invention provides adrive device for an electric vehicle, comprising: an electric motor; aspeed reduction unit including an input shaft driven by output of theelectric motor; a hub unit rotationally driven by an output member ofthe speed reduction unit; and a housing accommodating the electric motorand the speed reduction unit, wherein the input shaft of the speedreduction unit is supported by bearings provided at two locations in theaxial direction, the drive device being configured such that thebearings provided at the two locations are both supported by the outputmember, and the housing is provided with a suspension joining portion.

According to the above-described configuration, since the bearings forsupporting the input shaft at two locations in the axial direction areattached together to the output member, vibration and impact transmittedfrom the vehicle wheel to the output member will be imposed on both thebearings at the same time and in the same manner. As a result of this,both the bearings are prevented from being subjected to eccentric load.Moreover, the drive device for an electric vehicle can be attached tothe vehicle body by directly joining the above-described suspensionjoining portion to the vehicle body, and thus a knuckle as anintermediate part is not required.

The output member may be configured to include flanges disposed on bothsides in the axial direction of a speed reduction rotational member suchas a pinion gear so that the flanges are coupled and integrated witheach other by both end portions of a support pin of the speed reductionrotational member being secured to the flanges, and each of theabove-described bearings is placed between the inner radial surface ofeach flange and the input shaft.

The above-described “speed reduction rotational member” and “supportpin” correspond to the “pinion gear” and the “pinion pin” supporting thepinion gear respectively in the case of a planetary gear type. Byattaching each bearing to the inner radial surface of each of theabove-described flanges, it is possible to realize a configuration inwhich both bearings are attached together to the output member.

Since the above-described speed reduction unit has a configuration inwhich the flanges on both sides are coupled and integrated with eachother by support pins, the pinion gear can be placed between both theflanges.

Thus, the flanges can be configured to be coupled with each other by abridge so that the flanges can be securely coupled and integrated witheach other by the bridge.

Since both the flanges are securely engaged and integrated with eachother by the above-described bridge, the support stiffness of thesupport pin such as the pinion pin whose both end portions are coupledto both the flanges is increased. Moreover, by providing the bridge atmultiple locations of equally spaced positions in a circumferentialdirection of the flange, the rotation of the output member becomessmooth, and the rotational accuracy of the input shaft and the rotor ofthe electric motor fitted and secured to the input shaft is improved.

Advantageous Effects of Invention

As described so far, since the present invention is configured such thata pair of bearings supporting an input shaft of a speed reduction unitare both attached to an output member of the speed reduction unit, boththe bearings are prevented from being subjected to eccentric load. As aresult of this, the present invention can achieve the effects ofimproving the rotational accuracy of the input shaft and the durabilityof the bearings, and further suppressing the rotation noise of thebearings.

Moreover, since the suspension joining portion is provided in thehousing, there is no need of providing a knuckle on the vehicle bodyside, thus allowing reduction of the number of parts on the vehicle bodyside.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of Embodiment 1.

FIG. 2 is a partially enlarged cross sectional view of Embodiment 1.

FIG. 3 is an enlarged sectional view taken in X1-X1 line in FIG. 2.

FIG. 4 is a perspective view of a spacer shown in FIG. 3.

FIG. 5 is a cross sectional view taken in X2-X2 line in FIG. 1.

FIG. 6A is a cross sectional view of a variant of a speed reduction unitportion.

FIG. 6B is a cross sectional view taken in X3-X3 line of FIG. 6A.

FIG. 7 is a cross sectional view to show a part of Embodiment 2.

FIG. 8 is a cross sectional view of Embodiment 3.

FIG. 9 is a side view of Embodiment 3.

FIG. 10 is a partial cross sectional view of a variant of Embodiment 3.

DESCRIPTION OF EMBODIMENTS

Hereafter, embodiments of the present invention will be described basedon the appended drawings.

Embodiment 1

A drive device for an electric vehicle relating Embodiment 1 includes,as principal components, an electric motor 11, a speed reduction unit 12which is driven by the output power of the electric motor 11, a hub unit15 which is rotated by an output member 14 coaxial with an input shaft13 of the speed reduction unit 12, and a housing 16 which accommodatesthe electric motor 11 and the speed reduction unit 12, as shown in FIG.1.

The above-described housing 16 includes a cylindrical portion 17 and afront end portion 18 in the radial direction, which is provided at thefront end of the cylindrical portion (the end portion of an outboardside, or an end portion on the left side of the figure). A centralportion of the front end portion 18 is opened, and a rear end portion ofan outer member 21 of the hub unit 15 is fitted into an opening hole 19so that a flange 22 is secured to the front end portion 18 with a bolt23.

A partition base portion 18 a, which is concentric with the opening hole19 and has a larger diameter than that, is provided inside the front endportion 18 of the housing 16. A dish-shaped partition member 20 issecured to the partition base portion 18 a with a bolt 20 a. A centerhole 25 is provided at the center of the partition member 20. The centerhole 25 faces an outer radial surface of the input shaft 13 with a gapin a radial direction therebetween. A partition 24 is formed of theabove-described partition base portion 18 a and the partition member 20joined and secured thereto. The partition 24 has a function ofsectioning the interior of the housing 16 into an accommodation spacefor the electric motor 11 on the outer radial side, and an accommodationspace for the speed reduction unit 12 on the inner radial side.

A suspension joining portion 27 which projects in the axial direction isprovided at two centrosymmetric locations on a rear end edge of thecylindrical portion 17 of the housing 16. In a conventional automobile,the hub unit 15 is joined to the suspension with a knuckle of thevehicle body lying therebetween; however, in the present Embodiment 1,the suspension on the vehicle body side can be directly joined to thesuspension joining portion 27 which is a part of the housing 16.

Since the housing 16 will achieve the function of the knuckle, it can bedescribed as a structure in which the knuckle is integrated with thehousing 16. In this case, if the outer member 21 of the hub unit 15becomes necessary to be replaced, the replacement can be performedsimply by detaching the bolt 23 without need of detaching the housing 16from the suspension.

In the case shown in the figure, the electric motor 11 is aradial-gap-type brushless DC motor, and is made up of a stator 28secured to an inner radial surface of the cylindrical portion 17 of thehousing 16, and a rotor 29 disposed on an inner radial surface of thestator 28 with a radial gap. The rotor 29 is fitted and secured to theinput shaft 13 by a rotor support member 31.

The rotor support member 31 is made up of a support member cylindricalportion 31 a (see FIG. 2) fitted to an inner radial portion of the rotor29, and a support member disc portion 31 b which extends reward alongthe partition 24 and which is bent to the inner radial direction of thepartition. A boss portion 31 c is provided in an inner radial portion ofthe support member disc portion 31 b, and the boss portion 31 c isfitted to the input shaft 13 and secured to the input shaft 13 with akey locking portion 35.

The above-described boss portion 31 c is inserted into the inner radialside of the center hole 25 of the partition 24, and an oil seal member36 is placed between the center hole 25 and the boss portion 31 c (seeFIG. 2). The accommodation portion of the electric motor 11 and theaccommodation portion of the speed reduction unit 12 are partitioned andoil-sealed by the partition 24 and the oil seal member 36. As a resultof this, lubricant oil on the speed reduction unit 12 side is preventedfrom moving to the electric motor 11 side, and thus the electric motor11 side is kept dry, thus resolving the malfunction that the lubricantoil hinders the rotation of the rotor 29.

The speed reduction unit 12 is of a planetary gear type, and is made upof, as shown in FIG. 2, the input shaft 13, the output member 14, a sungear 39 which is attached to the outer radial surface of the input shaftwith a key locking portion 38, a ring gear 42 which is disposed along aninner radial surface of a partition cylindrical portion 24 b in theouter periphery of the sun gear 39, and which is attached with a keylocking portion 41, and pinion gears 43 which are disposed at threelocations equally spaced in the circumferential direction between thering gear 42 and the sun gear 39. The pinion gear 43 is supported by apinion pin 45 via a needle roller bearing 44.

The output member 14 includes a coupled shaft portion 47 at an endportion of an outboard side thereof. The coupled shaft portion 47 isspline-coupled to an inner member 46 of the hub unit 15 and secured by anut 50. A bearing support portion 49, which is formed to have a one-steplarger diameter than that of the coupled shaft portion 47, is providedon the inner end side of the coupled shaft portion 47.

On an inboard side of the output member 14, a pair of flanges 52 and 53which oppose each other in the axial direction are provided with aspacing slightly larger than the width of the pinion gear 43 in theaxial direction. A bridge 54 for joining the flanges 52 and 53 to eachother in the axial direction is provided at three locations of equallyspaced positions in the circumferential direction. The flanges 52 and 53have a function as a carrier in the speed reduction unit 12 of planetarygear type.

Providing the bridge 54 at equally spaced positions in thecircumferential direction allows the output member 14 to be smoothlyrotated, and moreover, to improve the rotational accuracy of the rotor29 of the electric motor 11 through the output member 14 and the inputshaft 13.

A shaft hole 51 which is coaxial with the coupled shaft portion 47 isprovided at the center of an end surface of the flange 53 of the inboardside. This shaft hole 51 has a length reaching the bearing supportportion 49.

There are provided pinion gear accommodation portions 55 at the threelocations, which are sectioned in the circumferential direction by thepair of the flanges 52 and 53 opposing each other in the axialdirection, and the bridges 54 at the three locations in thecircumferential direction (see FIG. 3). The pinion gear 43 isaccommodated in each pinion gear accommodation portion 55, and both endportions of the pinion pin 45 are inserted through the flanges 52 and53, respectively, and each secured by a locking screw 56. It can be saidthat both the flanges 52 and 53 are coupled and integrated with eachother not only by the bridge 54, but also by the pinion pin 45.

Since the flanges 52 and 53 are integrated with each other by the bridge54, the support stiffness at both ends of the pinion pin 45 increases.

A thrust plate 57 is placed between each side surface of each piniongear 43 and each of the flanges 52 and 53 to ensure smooth rotation ofthe pinion gear 43.

A pair of rolling bearings 58 and 59 for supporting the input shaft 13are provided on both sides of the sun gear 39 between an inner radialsurface of each of the flanges 52 and 53 and the outer radial surface ofthe input shaft 13 opposing each of the inner radial surfaces of theflanges 52 and 53. By adopting this configuration, the respectiverolling bearings 58 and 59 are supported together by the same outputmember 14.

Further, as shown in FIG. 2, the positional relationship in the axialdirection between each of the rolling bearings 58 and 59, and a fittingportion between the support member disc portion 31 b and the input shaft13 is such that the respective rolling bearings 58 and 59 are disposedtogether on the outboard side, and form a so-called cantilever supportstructure as the support structure for the input shaft 13.

In contrast to this, in the conventional art (Patent Literature 1),while the bearing on the outboard side is disposed on the outboard sidewith respect to the fitting portion between the support member discportion and the input shaft, the bearing on the inboard side is attachedto the housing, and therefore is located on the inboard side withrespect to the above-described fitting portion. Therefore, the supportstructure of the input shaft forms a so-called both-end supportstructure. The cantilever support structure is characterized by asimplified structure compared with the both-end support structure.

The above-described rolling bearing 58 on the outboard side isconfigured such that its inner ring is engaged with a stepped portion 61provided in the input shaft 13, and its outer ring is engaged with astepped portion 62 provided in an inner radial surface of the shaft hole51. The rolling bearing 59 on the inboard side is configured such thatits inner ring is engaged with the boss portion 31 c of the rotorsupport member 31 and the key locking portion 35, and its outer ring isengaged with a retaining ring 63.

The sun gear 39 is placed between the respective inner rings of therespective rolling bearings 58 and 59, and also a spacer 64 is placedbetween the outer rings. The spacer 64 prevents both the rollingbearings 58 and 59 from being displaced in a direction to approach toeach other.

The spacer 64 is formed into a cylindrical form as shown in FIGS. 3 and4, and is provided, at three locations in the circumferential direction,with window holes 65 which correspond to the shape of theabove-described pinion gear accommodation portion 55. Further, a closureportion 66 between the respective window holes 65 is formed into a shapecorresponding to the shape of the bottom plane of the above-describedbridge 54. The spacer 64 is placed between the rolling bearings 58 and59 on the inner radial surface of the shaft hole 51 in a posture thateach window hole 65 corresponds to the pinion gear accommodation portion55 (see FIG. 3), and is configured to be positioned by screwing asecuring screw 67 from an outer radial surface of the bridge 54 into apositioning hole 60 (see FIG. 4).

The above-described spacer 64 allows to control the bearingpressurization to be applied to both the rolling bearings 58 and 59 byappropriately setting the axial length thereof, thus providing a simplefixed-position pressurization structure.

When seen in the radial direction, the speed reduction unit 12 isradially disposed to be accommodated on the inner radial side of theelectric motor 11 with respect to the partition 24, and the size in theaxial direction is made compact compared with a case where the unit isdisposed in the axial direction.

Here, additionally describing the partition 24, the partitioncylindrical portion 24 b is placed between the electric motor 11 and thespeed reduction unit 12, which are disposed in the radial direction, anda partition disc portion 24 a is placed between the speed reduction unit12 and the support member disc portion 31 b. A peripheral edge portionof the center hole 25 faces the outer radial surface of the boss portion31 c of the rotor support member 31 with a predetermined spacingtherebetween. The ring gear 42 of the speed reduction unit 12 is securedto an inner radial surface of the partition base portion 18 a with thekey locking portion 41.

The oil seal member 36 is placed between the peripheral edge portion ofthe above-described center hole 25 and the boss portion 31 c. Theaccommodation space for the electric motor 11 of the housing 16 and theaccommodation space for the speed reduction unit 12 are partitioned bythe presence of the oil seal member 36 and the partition 24. Since, as aresult of this, the lubricant oil on the speed reduction unit 12 side isprevented from moving to the electric motor 11 side, and thus theelectric motor side is kept dry, the lubricant oil is prevented fromhindering the rotation of the rotor 29.

Although, it is described above that both the flanges 52 and 53 of theoutput member 14 are coupled and integrated by both the bridge 54 andthe pinion pin 45, it is possible to take a structure in which theflange 53 is configured to be a separate body from the output member 14and both are coupled and integrated by the pinion pin 45, as shown inFIGS. 6A and 6B.

An oil filler port 68 and an oil drainage port 69 for lubricant oil tolubricate the interior of the speed reduction unit 12 are provided inthe front end portion of the housing 16. The lubricant oil is sealed bythe above-described oil seal member 36 on the electric motor 11 side,and is sealed by an oil seal member 70, which is placed between thebearing support portion 49 of the output member 14 and the outer member21, on the hub unit 15 side. The oil filler port 68 and the oil drainageport 69 are blocked by a blocking screw 72.

Since the electric motor 11 and the speed reduction unit 12, exceptingthe rear end portion (the end portion of the inboard side) of the inputshaft 13, fit in the range of the axial length of the cylindricalportion 17 of the housing 16 as shown in FIG. 1, a rear cover 73 isfitted to the rear end portion of the cylindrical portion 17 via a sealmember 60. A fin 74 for heat dissipation is provided on an outer sidesurface of the rear cover 73 so that heat of the electric motor 11 isdissipated to the outside.

A rotation angle sensor 75 is provided between the center hole of therear cover 73 and the input shaft 13 that passes through the centerhole, and that portion is covered by a sensor cover 77. The rotationangle sensor 75 shown is a resolver, and whose sensor stator 75 a issecured into the center hole of the rear cover 73, and a sensor rotor 75b is attached to the input shaft 13.

A lead wire 83 of the sensor stator 75 a is connected to a connectorinsertion portion 78 provided outside the sensor cover 77. As therotation angle sensor 75, a Hall element can be used besides theabove-described resolver.

A rotational angle of the input shaft 13 detected by the rotation anglesensor 75 is inputted to a control circuit, which is omitted fromshowing, via the above-described signal wire cable to be used for therotational control of the electric motor 11.

A power supply terminal box 76 for providing power supply to the stator28 of the electric motor 11 is provided at a position decentered towardan outer peripheral edge of the above-described rear cover 73, and at aposition 90 degrees different from the above-described suspensionjoining portion 27 (see FIG. 5).

The power supply terminal box 76 is formed into a cylindrical shape thatpasses through the rear cover 73, and is provided with a working hole 80in an outer peripheral portion of the box. The working hole 80 isusually blocked by a cover 81. A power supply terminal 82 is providedinside the box at a position opposing the working hole 80. A lead wire83 connected to the winding of the stator 28 is connected to the powersupply terminal 82, and also a connection terminal of a power supplycable 84 is connected to the same power supply terminal 82. These aresecured by fastening screws 85. A cable hole 84 a is provided at a rearend of the power supply terminal box 76 and the power supply cable 84 isinserted therethrough.

The hub unit 15 is made up of, as shown in FIG. 1, the above-describedinner member 46 which is integrated with a hub 86, a pair of inner rings87 that are fitted to an outer radial surface of the inner member 46,the outer member 21 having the flange 22, an outer ring 88 fitted to aninner radial surface of the outer member 21 and having multiple rows oftracks, and multiple rows of balls 89 to be placed between the innerring 87 and the outer ring 88. The vehicle wheel is attached to the hub86 with hub bolts 90.

The coupled shaft portion 47 of the output member 14 is spline-coupledto an inner radial surface of the inner member 46, and a tip end portionof the coupled shaft portion 47 projecting to the outside from the innermember 46 is secured by the nut 50 as described above. In place of thesecuring means using the nut 50, securing means such as press cut joint,diameter expansion caulking, and swing caulking may be adopted.

Although the above-described hub unit 15 is of a form of so-called firstgeneration, those of a form of the second generation or third generationmay be used.

The driving device for an electric vehicle of Embodiment 1 is configuredas described above, and next, the operation thereof will be described.

When the electric motor 11 is driven by an accelerator at the drivingseat being activated, the input shaft 13 is rotated integrally with therotation of the rotor 29, and a motor output is inputted to the speedreduction unit 12. In the speed reduction unit 12, when the sun gear 39rotates integrally with the input shaft 13, the pinion gears 43 revolvearound the sun gear 39 while rotating on their own axes. Each of thepinion pins 45 performs speed-reduced rotation at its revolving speed,and thereby rotates the output member 14 at a speed-reduced output shownby the above-described speed reduction ratio.

The inner member 46 of the hub unit 15 is rotated integrally with thecoupled shaft portion 47 of the output member 14, thereby driving thewheel attached to the hub 86.

The above-described input shaft 13 rotates by being supportedrespectively by the rolling bearing 58 on the outboard side and therolling bearing 59 on the inboard side at both sides of the pinion gear43. Since these rolling bearings 58 and 59 are both attached to therespective flanges 52 and 53 (respective flanges 52 and 53 which areintegrated via the pinion pin 45 in the case of FIGS. 6A and 6B) whichare each integrated with the output member 14, vibration and impact inthe radial direction which are transmitted from the wheel to the outputmember 14 through the hub unit 15 is imposed onto both the rollingbearings 58 and 59 at the same time and in the same manner.

Since, as a result of that, both the rolling bearings 58 and 59 can beprevented from being subjected to eccentric load, it is possible toimprove the rotational accuracy and durability, and suppress therotation noise.

Since the pinion pin 45 of the pinion gear 43 is supported at both endportions thereof by the respective flanges 52 and 53, the supportstiffness increases compared with a conventional case where it iscantilevered.

The above-described rolling bearings 58 and 59 are disposed on theoutboard side with respect to the fitting portion between the rotorsupport member 31 of the rotor 29 and the input shaft 13, that is, thekey locking portion 35, so that the support structure becomes simple andeasy to be assembled compared with a conventional case where thebearings are disposed on both sides thereof.

Further, since the lubricant oil in the speed reduction unit 12 issealed on the electric motor 11 side by the oil seal member 36, andsealed on the hub unit 15 side by the oil seal member 70, leakage on theelectric motor 11 side and the hub unit side is prevented. As a resultof that, on the electric motor 11 side, rotation of the rotor 29 is nothindered, and on the hub unit 15 side, leakage of the lubricant oil tothe outside through the hub unit 15 is prevented.

The heat generated in association with the driving of the electric motor11 is effectively dissipated by the fin 74 of the rear cover 73.

The rotational angle of the input shaft 13, which is necessary for therotational control of the electric motor 11, is detected by the rotationangle sensor 75 and inputted to the control apparatus.

Embodiment 2

Embodiment 2 shown in FIG. 7 differs in the configuration of the hubunit 15 compared with the above-described Embodiment 1. That is, theflange 22 of the outer member 21 of the hub unit 15 in this case isformed to have a larger diameter than that of the flange 22 (see FIG. 1)of the above-described Embodiment 1.

A flange cylindrical portion 32 projecting in the axial direction isprovided in the inner side surface of the flange 22 with a largerdiameter. The flange cylindrical portion 32 extends over an outer radialsurface of the flange 53 on the outboard side of the output member 14.The flange cylindrical portion 32 is fitted to an inner radial surfaceof the opening hole 19 of the front end portion 18 of the housing 16.

Since, compared with the case of Embodiment 1, the opening hole 19 isformed to have a large inner diameter, it is easy to fabricate thepartition 24 which is integrated with the front end portion 18, in thecase of this Embodiment 2. For this reason, in the case of Embodiment 2,the partition member 20 (see FIG. 1) which is a separate member is notused.

A ball of a hub bearing 89 a on the outboard side is placed between atrack groove formed in the outer radial surface of the inner member 46,and a track groove formed in the inner radial surface of the outermember 21. Moreover, the ball of the hub bearing 89 b on the inboardside is placed between a track surface formed in the outer radialsurface of the flange 52 and a track groove formed in an inner radialsurface of the flange cylindrical portion 32.

Letting the radii from “the center” of the ball center of the hubbearing 89 a on the outboard side, the center of the pinion shaft 45,and the ball center of the hub bearing 89 b on the inboard side be r1,r2, and r3, respectively, these sizes have a relationship as r1<r3, andr2<r3. Other configurations are the same as those of the case ofEmbodiment 1.

As describe above, setting the ball PCD (pitch circle diameter) of thehub bearing 89 b on the inboard side to be larger than the ball PCD ofthe hub bearing 89 a on the outboard side results in increasing in thebearing stiffness of the hub unit 15.

It is noted that the hub unit 15 in this case can be said to be avariant form of the so-called third generation.

Although, in the illustrated case, each of the balls of the hub bearings89 a and 89 b is configured to be in direct contact with the trackgroove, it is also possible to configure such that a bearing in whichthe track groove is provided in each of its inner ring and outer ringsis used, and these track rings are fitted to the aforementioned oppositemembers.

Embodiment 3

Embodiment 3 shown in FIGS. 8 to 10 differs from Embodiment 1 in theconfigurations of the hub unit 15, the rotation angle sensor 75, thepower supply terminal box 76, and the connector insertion portion 78.

That is, the hub unit 15 in this case is formed such that the flange 22of the outer member 21 has a larger diameter than in the case ofEmbodiment 1. For this reason, there is no need of adopting asupplementary housing 16 b as in Embodiment 1, and the single housing 16which has a similar structure to that of a main housing 16 a is used.The flange 22 with a larger diameter is secured to the housing 16 withthe bolt 23.

The ball 89 a on the outboard side constituting the hub bearing isplaced between the track groove provided in the outer radial surface ofthe inner member 46 and the track groove provided in the inner radialsurface of the outer member 21. Further, the ball 89 b on the inboardside is placed between the track groove provided in the outer radialsurface of the output member 14 and the track groove provided in theinner radial surface of the outer member 21. It can be said to be avariant type of the so-called third-generation.

The rotation angle sensor 75 is provided between opposite surfaces inthe axial direction of the support member disc portion 31 b of the rotorsupport member 31, and the partition disc portion 24 a. A sensor rotor91 a is made up of a magnet which is attached to the support member discportion 31 b with a vis 92. Moreover, a sensor stator 91 b is made up ofa Hall element attached to the opposite surface of the partition discportion 24 a with a vis 93. Both oppose each other via an axial gap.

As shown in FIG. 10, the cross sectional shape of the sensor rotor 91 bmay be formed into a reverse L-shape, and a radial gap may be formedbetween the horizontal portion of the sensor rotor 91 b and the sensorstator 91 a.

The power supply terminal box 76 and the connector insertion portion 78are both provided in the housing 16 (see FIG. 9). The power supplyterminal box 76 is configured such that an accommodation recessedportion 94 is provided within the range of the wall thickness of a rearend surface of the housing 16, and the power supply terminal 82 isprovided inside the accommodation recessed portion 94. A communicationhole 95 in communication with the interior of the housing 16 is providedin a deep part of the accommodation recessed portion 94. The openingsurface of the accommodation recessed portion 94 is blocked by a covermember 96. The cover member 96 is provided with a cable hole 97 forpassing the power supply cable 84.

Further, the working hole 80 is provided in the wall surface of thehousing 16. This working hole 80 is usually blocked by the cover 81. Thelead wire 83 on the electric motor 11 side is connected to the powersupply terminal 82 through the communication hole 95, and the powersupply cable 84 is drawn in through the cable hole 97 so that itsconnection terminal is connected to the power supply terminal 82. Bothare coupled to the power supply terminal 82 with a fastening screw 85.

The connector insertion portion 78 is provided in the rear end surfaceof the housing 16 side-by-side with the power supply terminal box 76, asshown in FIG. 9. The connector insertion portion 78 is configured suchthat a recessed portion 99 is provided in the rear end surface of thehousing 16, and a lead wire hole 100 which brings a deep part of therecessed portion 99 and the interior of the housing 16 intocommunication is provided (see FIG. 8). A lead wire 101 of the rotationangle sensor 75 is connected to the interior of the recessed portion 99through the lead wire hole 100. The connector (not shown) of the signalcable is inserted into the connector insertion portion 78.

As described above, the configuration in which both the power supplyterminal box 76 and the connector insertion portion 78 are provided inthe housing 16 can simplify the configuration of the rear cover 73 sothat it can be made up of a thin metal plate, a plastic plate, and thelike.

REFERENCE SIGNS LIST

-   11 Electric motor-   12 Speed reduction unit-   13 Input shaft-   14 Output member-   15 Hub unit-   16 Housing-   17 Cylindrical portion-   18 Front end portion-   18 a Partition base portion-   19 Opening hole-   20 Partition member-   20 a Bolt-   21 Outer member-   22 Flange-   23 Bolt-   24 Partition-   24 a Partition disc portion-   24 b Partition cylindrical portion-   25 Center hole-   26 Fin-   27 Suspension joining portion-   28 Stator-   29 Rotor-   31 Rotor support member-   31 a Support member cylindrical portion-   31 b Support member disc portion-   31 c Boss portion-   32 Flange cylindrical portion-   35 Key locking portion-   36 Oil seal member-   38 Key locking portion-   39 Sun gear-   41 Key locking portion-   42 Ring gear-   43 Pinion gear-   44 Needle roller bearing-   45 Pinion pin-   46 Inner member-   47 Coupled shaft portion-   48 Rolling bearing-   49 Bearing support portion-   50 Nut-   51 Shaft hole-   52, 53 Flange-   54 Bridge-   55 Pinion gear accommodation portion-   56 Locking screw-   57 Thrust plate-   58, 59 Rolling bearing-   60 Positioning hole-   61, 62 Stepped portion-   63 Retaining ring-   64 Spacer-   65 Window hole-   66 Closure portion-   67 Securing screw-   68 Oil filler port-   69 Oil drainage port-   79 Oil seal member-   71 Groove-   72 Blocking screw-   73 Rear cover-   74 Fin-   75 Rotation angle sensor-   75 a Sensor stator-   75 b Sensor rotor-   76 Power supply terminal box-   76 a Power supply terminal-   77 Sensor cover-   78 Connector insertion portion-   79 Insertion hole-   80 Working hole-   81 Cover-   82 Power supply terminal-   83 Lead wire-   84 Power supply cable-   84 a Cable hole-   85 Fastening screw-   86 Hub-   87 Inner ring-   88 Outer ring-   89 Ball-   89 a, 89 b Hub bearing-   90 Hub bolt-   91 a Sensor rotor-   91 b Sensor stator-   92, 93 Vis-   94 Accommodation recessed portion-   95 Communication hole-   96 Cover member-   97 Cable hole-   99 Recessed portion-   100 Lead wire hole

1. A drive device for an electric vehicle, comprising: an electricmotor; a speed reduction unit including an input shaft driven by outputof the electric motor; a hub unit rotationally driven by an outputmember of the speed reduction unit; and a housing accommodating theelectric motor and the speed reduction unit, wherein the input shaft ofthe speed reduction unit is supported by bearings provided at twolocations in the axial direction, the drive device for an electricvehicle being configured such that the bearings provided at the twolocations are both supported by the output member, and the housing isprovided with a suspension joining portion.
 2. The drive device for anelectric vehicle according to claim 1, wherein the suspension joiningportion is provided at two centrosymmetric locations on a rear end edgeof the housing.
 3. The drive device for an electric vehicle according toclaim 1, wherein the output member supports a pair of bearings.
 4. Thedrive device for an electric vehicle according to claim 3, comprising asupport structure in which the pair of bearings that support the inputshaft are both disposed on an outboard side of a fitting portion betweenthe input shaft and the rotor support member of the electric motor. 5.The drive device for an electric vehicle according to claim 3, whereinthe output member has a pair of flanges which are disposed on both sidesin an axial direction of a speed reduction rotational member of thespeed reduction unit, the flanges are coupled and integrated with eachother by both end portions of a support pin of the speed reductionrotational member being secured to each flange, and each of the bearingsis placed between an inner radial surface of each flange and the inputshaft.
 6. The drive device for an electric vehicle according to claim 5,wherein the speed reduction unit is of a planetary gear type which ismade up of a sun gear and a ring gear, which are provided coaxially withthe input shaft, a plurality of pinion gears which are provided atequally spaced positions in a circumferential direction between the sungear and the ring gear, and a carrier for holding the pinion gears. 7.The drive device for an electric vehicle according to claim 6, whereinthe speed reduction unit is of the planetary gear type, and the flangesare integrated with each other by bridges provided at a required spacingin a circumferential direction, the pinion gears are accommodatedbetween the respective bridges, and both end portions of the pinion pinare supported by the flanges, respectively.
 8. The drive device for anelectric vehicle according to claim 3, wherein the pair of bearings areeach made up of a rolling bearing; a ring-shaped spacer is placedbetween outer rings of the pair of rolling bearings; the spacer isprovided with a window hole in a portion which opposes the speedreduction rotational member, where the window hole is for the purpose ofavoiding interference; and a fixing vis of the spacer is screwed from anouter radial surface of the bridge.
 9. The drive device for an electricvehicle according to claim 3, wherein the speed reduction unit isdisposed on an inner diameter side of the electric motor, and theaccommodation portions of the speed reduction unit and the electricmotor are sectioned by the partition provided in the housing.
 10. Thedrive device for an electric vehicle according to claim 9, wherein thepartition is made up of a partition base portion which is provided inthe housing, and a partition member which is joined and secured to thepartition base portion.
 11. The drive device for an electric vehicleaccording to claim 10, wherein a stator of the electric motor is securedto the housing on the outer diameter side of the speed reduction unit, arotor is disposed between the stator and the partition, and a supportmember of the rotor is fitted to and integrated with the input shaft.12. The drive device for an electric vehicle according to claim 3,wherein a flange of an outer member of the hub unit is secured to thehousing accommodating the electric motor and the speed reduction unit.